#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more 
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership. 
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with 
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion

using log4net.Core;
using log4net.Util;
using System;
using System.Globalization;
using System.Text;

namespace log4net.Appender
{
    /// <summary>
    /// Appends logging events to the terminal using ANSI color escape sequences.
    /// </summary>
    /// <remarks>
    /// <para>
    /// AnsiColorTerminalAppender appends log events to the standard output stream
    /// or the error output stream using a layout specified by the 
    /// user. It also allows the color of a specific level of message to be set.
    /// </para>
    /// <note>
    /// This appender expects the terminal to understand the VT100 control set 
    /// in order to interpret the color codes. If the terminal or console does not
    /// understand the control codes the behavior is not defined.
    /// </note>
    /// <para>
    /// By default, all output is written to the console's standard output stream.
    /// The <see cref="Target"/> property can be set to direct the output to the
    /// error stream.
    /// </para>
    /// <para>
    /// NOTE: This appender writes each message to the <c>System.Console.Out</c> or 
    /// <c>System.Console.Error</c> that is set at the time the event is appended.
    /// Therefore it is possible to programmatically redirect the output of this appender 
    /// (for example NUnit does this to capture program output). While this is the desired
    /// behavior of this appender it may have security implications in your application. 
    /// </para>
    /// <para>
    /// When configuring the ANSI colored terminal appender, a mapping should be
    /// specified to map a logging level to a color. For example:
    /// </para>
    /// <code lang="XML" escaped="true">
    /// <mapping>
    /// 	<level value="ERROR" />
    /// 	<foreColor value="White" />
    /// 	<backColor value="Red" />
    ///     <attributes value="Bright,Underscore" />
    /// </mapping>
    /// <mapping>
    /// 	<level value="DEBUG" />
    /// 	<backColor value="Green" />
    /// </mapping>
    /// </code>
    /// <para>
    /// The Level is the standard log4net logging level and ForeColor and BackColor can be any
    /// of the following values:
    /// <list type="bullet">
    /// <item><term>Blue</term><description></description></item>
    /// <item><term>Green</term><description></description></item>
    /// <item><term>Red</term><description></description></item>
    /// <item><term>White</term><description></description></item>
    /// <item><term>Yellow</term><description></description></item>
    /// <item><term>Purple</term><description></description></item>
    /// <item><term>Cyan</term><description></description></item>
    /// </list>
    /// These color values cannot be combined together to make new colors.
    /// </para>
    /// <para>
    /// The attributes can be any combination of the following:
    /// <list type="bullet">
    /// <item><term>Bright</term><description>foreground is brighter</description></item>
    /// <item><term>Dim</term><description>foreground is dimmer</description></item>
    /// <item><term>Underscore</term><description>message is underlined</description></item>
    /// <item><term>Blink</term><description>foreground is blinking (does not work on all terminals)</description></item>
    /// <item><term>Reverse</term><description>foreground and background are reversed</description></item>
    /// <item><term>Hidden</term><description>output is hidden</description></item>
    /// <item><term>Strikethrough</term><description>message has a line through it</description></item>
    /// </list>
    /// While any of these attributes may be combined together not all combinations
    /// work well together, for example setting both <i>Bright</i> and <i>Dim</i> attributes makes
    /// no sense.
    /// </para>
    /// </remarks>
    /// <author>Patrick Wagstrom</author>
    /// <author>Nicko Cadell</author>
    public class AnsiColorTerminalAppender : AppenderSkeleton
    {
        #region Colors Enum

        /// <summary>
        /// The enum of possible display attributes
        /// </summary>
        /// <remarks>
        /// <para>
        /// The following flags can be combined together to
        /// form the ANSI color attributes.
        /// </para>
        /// </remarks>
        /// <seealso cref="AnsiColorTerminalAppender" />
        [Flags]
        public enum AnsiAttributes : int
        {
            /// <summary>
            /// text is bright
            /// </summary>
            Bright = 1,
            /// <summary>
            /// text is dim
            /// </summary>
            Dim = 2,

            /// <summary>
            /// text is underlined
            /// </summary>
            Underscore = 4,

            /// <summary>
            /// text is blinking
            /// </summary>
            /// <remarks>
            /// Not all terminals support this attribute
            /// </remarks>
            Blink = 8,

            /// <summary>
            /// text and background colors are reversed
            /// </summary>
            Reverse = 16,

            /// <summary>
            /// text is hidden
            /// </summary>
            Hidden = 32,

            /// <summary>
            /// text is displayed with a strikethrough
            /// </summary>
            Strikethrough = 64
        }

        /// <summary>
        /// The enum of possible foreground or background color values for 
        /// use with the color mapping method
        /// </summary>
        /// <remarks>
        /// <para>
        /// The output can be in one for the following ANSI colors.
        /// </para>
        /// </remarks>
        /// <seealso cref="AnsiColorTerminalAppender" />
        public enum AnsiColor : int
        {
            /// <summary>
            /// color is black
            /// </summary>
            Black = 0,

            /// <summary>
            /// color is red
            /// </summary>
            Red = 1,

            /// <summary>
            /// color is green
            /// </summary>
            Green = 2,

            /// <summary>
            /// color is yellow
            /// </summary>
            Yellow = 3,

            /// <summary>
            /// color is blue
            /// </summary>
            Blue = 4,

            /// <summary>
            /// color is magenta
            /// </summary>
            Magenta = 5,

            /// <summary>
            /// color is cyan
            /// </summary>
            Cyan = 6,

            /// <summary>
            /// color is white
            /// </summary>
            White = 7
        }

        #endregion

        #region Public Instance Constructors

        /// <summary>
        /// Initializes a new instance of the <see cref="AnsiColorTerminalAppender" /> class.
        /// </summary>
        /// <remarks>
        /// The instance of the <see cref="AnsiColorTerminalAppender" /> class is set up to write 
        /// to the standard output stream.
        /// </remarks>
        public AnsiColorTerminalAppender()
        {
        }

        #endregion Public Instance Constructors

        #region Public Instance Properties

        /// <summary>
        /// Target is the value of the console output stream.
        /// </summary>
        /// <value>
        /// Target is the value of the console output stream.
        /// This is either <c>"Console.Out"</c> or <c>"Console.Error"</c>.
        /// </value>
        /// <remarks>
        /// <para>
        /// Target is the value of the console output stream.
        /// This is either <c>"Console.Out"</c> or <c>"Console.Error"</c>.
        /// </para>
        /// </remarks>
        virtual public string Target
        {
            get { return m_writeToErrorStream ? ConsoleError : ConsoleOut; }
            set
            {
                string trimmedTargetName = value.Trim();

                if (string.Compare(ConsoleError, trimmedTargetName, true, CultureInfo.InvariantCulture) == 0)
                {
                    m_writeToErrorStream = true;
                }
                else
                {
                    m_writeToErrorStream = false;
                }
            }
        }

        /// <summary>
        /// Add a mapping of level to color
        /// </summary>
        /// <param name="mapping">The mapping to add</param>
        /// <remarks>
        /// <para>
        /// Add a <see cref="LevelColors"/> mapping to this appender.
        /// Each mapping defines the foreground and background colours
        /// for a level.
        /// </para>
        /// </remarks>
        public void AddMapping(LevelColors mapping)
        {
            m_levelMapping.Add(mapping);
        }

        #endregion Public Instance Properties

        #region Override implementation of AppenderSkeleton

        /// <summary>
        /// This method is called by the <see cref="AppenderSkeleton.DoAppend(LoggingEvent)"/> method.
        /// </summary>
        /// <param name="loggingEvent">The event to log.</param>
        /// <remarks>
        /// <para>
        /// Writes the event to the console.
        /// </para>
        /// <para>
        /// The format of the output will depend on the appender's layout.
        /// </para>
        /// </remarks>
        override protected void Append(log4net.Core.LoggingEvent loggingEvent)
        {
            string loggingMessage = RenderLoggingEvent(loggingEvent);

            // see if there is a specified lookup.
            LevelColors levelColors = m_levelMapping.Lookup(loggingEvent.Level) as LevelColors;
            if (levelColors != null)
            {
                // Prepend the Ansi Color code
                loggingMessage = levelColors.CombinedColor + loggingMessage;
            }

            // on most terminals there are weird effects if we don't clear the background color
            // before the new line.  This checks to see if it ends with a newline, and if
            // so, inserts the clear codes before the newline, otherwise the clear codes
            // are inserted afterwards.
            if (loggingMessage.Length > 1)
            {
                if (loggingMessage.EndsWith("\r\n") || loggingMessage.EndsWith("\n\r"))
                {
                    loggingMessage = loggingMessage.Insert(loggingMessage.Length - 2, PostEventCodes);
                }
                else if (loggingMessage.EndsWith("\n") || loggingMessage.EndsWith("\r"))
                {
                    loggingMessage = loggingMessage.Insert(loggingMessage.Length - 1, PostEventCodes);
                }
                else
                {
                    loggingMessage = loggingMessage + PostEventCodes;
                }
            }
            else
            {
                if (loggingMessage[0] == '\n' || loggingMessage[0] == '\r')
                {
                    loggingMessage = PostEventCodes + loggingMessage;
                }
                else
                {
                    loggingMessage = loggingMessage + PostEventCodes;
                }
            }

#if NETCF_1_0
			// Write to the output stream
			Console.Write(loggingMessage);
#else
            if (m_writeToErrorStream)
            {
                // Write to the error stream
                Console.Error.Write(loggingMessage);
            }
            else
            {
                // Write to the output stream
                Console.Write(loggingMessage);
            }
#endif

        }

        /// <summary>
        /// This appender requires a <see cref="Layout"/> to be set.
        /// </summary>
        /// <value><c>true</c></value>
        /// <remarks>
        /// <para>
        /// This appender requires a <see cref="Layout"/> to be set.
        /// </para>
        /// </remarks>
        override protected bool RequiresLayout
        {
            get { return true; }
        }

        /// <summary>
        /// Initialize the options for this appender
        /// </summary>
        /// <remarks>
        /// <para>
        /// Initialize the level to color mappings set on this appender.
        /// </para>
        /// </remarks>
        public override void ActivateOptions()
        {
            base.ActivateOptions();
            m_levelMapping.ActivateOptions();
        }

        #endregion Override implementation of AppenderSkeleton

        #region Public Static Fields

        /// <summary>
        /// The <see cref="AnsiColorTerminalAppender.Target"/> to use when writing to the Console 
        /// standard output stream.
        /// </summary>
        /// <remarks>
        /// <para>
        /// The <see cref="AnsiColorTerminalAppender.Target"/> to use when writing to the Console 
        /// standard output stream.
        /// </para>
        /// </remarks>
        public const string ConsoleOut = "Console.Out";

        /// <summary>
        /// The <see cref="AnsiColorTerminalAppender.Target"/> to use when writing to the Console 
        /// standard error output stream.
        /// </summary>
        /// <remarks>
        /// <para>
        /// The <see cref="AnsiColorTerminalAppender.Target"/> to use when writing to the Console 
        /// standard error output stream.
        /// </para>
        /// </remarks>
        public const string ConsoleError = "Console.Error";

        #endregion Public Static Fields

        #region Private Instances Fields

        /// <summary>
        /// Flag to write output to the error stream rather than the standard output stream
        /// </summary>
        private bool m_writeToErrorStream = false;

        /// <summary>
        /// Mapping from level object to color value
        /// </summary>
        private LevelMapping m_levelMapping = new LevelMapping();

        /// <summary>
        /// Ansi code to reset terminal
        /// </summary>
        private const string PostEventCodes = "\x1b[0m";

        #endregion Private Instances Fields

        #region LevelColors LevelMapping Entry

        /// <summary>
        /// A class to act as a mapping between the level that a logging call is made at and
        /// the color it should be displayed as.
        /// </summary>
        /// <remarks>
        /// <para>
        /// Defines the mapping between a level and the color it should be displayed in.
        /// </para>
        /// </remarks>
        public class LevelColors : LevelMappingEntry
        {
            private AnsiColor m_foreColor;
            private AnsiColor m_backColor;
            private AnsiAttributes m_attributes;
            private string m_combinedColor = "";

            /// <summary>
            /// The mapped foreground color for the specified level
            /// </summary>
            /// <remarks>
            /// <para>
            /// Required property.
            /// The mapped foreground color for the specified level
            /// </para>
            /// </remarks>
            public AnsiColor ForeColor
            {
                get { return m_foreColor; }
                set { m_foreColor = value; }
            }

            /// <summary>
            /// The mapped background color for the specified level
            /// </summary>
            /// <remarks>
            /// <para>
            /// Required property.
            /// The mapped background color for the specified level
            /// </para>
            /// </remarks>
            public AnsiColor BackColor
            {
                get { return m_backColor; }
                set { m_backColor = value; }
            }

            /// <summary>
            /// The color attributes for the specified level
            /// </summary>
            /// <remarks>
            /// <para>
            /// Required property.
            /// The color attributes for the specified level
            /// </para>
            /// </remarks>
            public AnsiAttributes Attributes
            {
                get { return m_attributes; }
                set { m_attributes = value; }
            }

            /// <summary>
            /// Initialize the options for the object
            /// </summary>
            /// <remarks>
            /// <para>
            /// Combine the <see cref="ForeColor"/> and <see cref="BackColor"/> together
            /// and append the attributes.
            /// </para>
            /// </remarks>
            public override void ActivateOptions()
            {
                base.ActivateOptions();

                StringBuilder buf = new StringBuilder();

                // Reset any existing codes
                buf.Append("\x1b[0;");

                // set the foreground color
                buf.Append(30 + (int)m_foreColor);
                buf.Append(';');

                // set the background color
                buf.Append(40 + (int)m_backColor);

                // set the attributes
                if ((m_attributes & AnsiAttributes.Bright) > 0)
                {
                    buf.Append(";1");
                }
                if ((m_attributes & AnsiAttributes.Dim) > 0)
                {
                    buf.Append(";2");
                }
                if ((m_attributes & AnsiAttributes.Underscore) > 0)
                {
                    buf.Append(";4");
                }
                if ((m_attributes & AnsiAttributes.Blink) > 0)
                {
                    buf.Append(";5");
                }
                if ((m_attributes & AnsiAttributes.Reverse) > 0)
                {
                    buf.Append(";7");
                }
                if ((m_attributes & AnsiAttributes.Hidden) > 0)
                {
                    buf.Append(";8");
                }
                if ((m_attributes & AnsiAttributes.Strikethrough) > 0)
                {
                    buf.Append(";9");
                }

                buf.Append('m');

                m_combinedColor = buf.ToString();
            }

            /// <summary>
            /// The combined <see cref="ForeColor"/>, <see cref="BackColor"/> and
            /// <see cref="Attributes"/> suitable for setting the ansi terminal color.
            /// </summary>
            internal string CombinedColor
            {
                get { return m_combinedColor; }
            }
        }

        #endregion // LevelColors LevelMapping Entry
    }
}
